1. Field of the Invention
The present invention relates generally to transport trailers and, more particularly, to a trailer adapted for use in transporting large specialized vehicles such as farm tractors, combines, and other agricultural machinery.
2. Discussion of the Prior Art
As disclosed in U.S. Pat. No. 4,125,198 to Donald R. Landoll, it is known to provide a trailer having an undercarriage that is shiftable longitudinally relative to a bed of the trailer between a rear, roading position wherein the bed is supported in a lowered, low-to-the-ground orientation, and a forward loading position wherein the bed is raised to a height sufficient to permit unrestricted shifting of the undercarriage in the longitudinal direction of the bed.
Although this conventional construction is effective in providing a trailer presenting a small loading angle while at the same time having the ability to assume a low profile for transport of tall loads, it would be desirable to provide an improved construction of a trailer which would have a prolonged life as compared with the normal useful life of the conventional design.
In the conventional trailer, as disclosed in U.S. Pat. No. 4,125,198, a pair of I-beams are provided, each including a lower flange defining a tracking surface. The undercarriage is provided with a pair of roller assemblies each in tracking engagement with the lower flange of one of the I-beams. Ramps are formed in the lower flanges and are adapted to receive particular rollers of the roller assemblies when the undercarriage is moved to the roading position.
Over prolonged periods of use of the conventional construction, it is possible that each of the lower flanges will begin to bend upward on either side of the associated web under the repetitive application of pressure to the flanges by the rollers. This phenomenon is termed "roll-up". Once roll-up of the flanges begins to occur, contact between the rollers and the tracking surface becomes uneven, with the inside edges of the rollers tending to exert more pressure on the flanges than the outside edges of the rollers. Thus, roller travel along the flanges is complicated, requiring additional power in order to move the undercarriage between positions. Further, in the extreme case, it is possible that the inside edges of the rollers could actually cut into the flanges causing them to weaken and ultimately fracture.